This randomized controlled clinical trial will evaluate and compare the efficacy and safety of intradermal injection of exosomes, platelet-rich plasma, and corticosteroid in patients with post-herpetic neuralgia. Forty-five adult patients with dermatomal pain persisting for at least 90 days after herpes zoster will be enrolled from outpatient clinics. Participants will be assigned to one of three groups: intradermal exosome injection, intradermal autologous platelet-rich plasma injection, or intradermal triamcinolone acetonide injection. Each group will receive four treatment sessions every two weeks. Outcomes will include pain severity, neuropathic pain characteristics, quality of life, patient satisfaction, and adverse effects, assessed at baseline, at the final session, and during follow-up visits at 3 and 6 months after the last session.

Inclusion Criteria:

• Patients with post-herpes zoster persistent dermatomal pain consistent with post-herpetic neuralgia for at least 90 days.

Male or female patients. Age 18 years or older. Willingness to comply with study procedures and attend follow-up visits. Ability and willingness to provide written informed consent

Exclusion Criteria:

• History of hypersensitivity to any of the study treatments. Pregnancy. Any type of skin infection involving the affected dermatome. Immunocompromised patients, including patients with cancer or HIV. Patients with bone marrow aplasia. Patients with known bleeding tendency, platelet dysfunction, or thrombocytopenia, defined as platelet count less than 150 × 10⁹/L.

Regular use of anticoagulant or antiplatelet drugs.

Open-label study; participants and investigators are not masked to treatment assignment.